The former US Secretary of State Condoleezza Rice has been drafted in to advise HSBC on the future location of its headquarters even as the bank's board has ruled out a move across the Atlantic.

Sky News understands that Ms Rice is among a number of global political figures who have been asked by HSBC's board to provide advice about the geopolitical context of its looming decision.

Europe's biggest bank has said it will provide an update on its review when it reports annual results next month, but insiders say that HSBC is keen to announce a firm decision that day, which falls ten months after it said it would look at leaving London.

Ms Rice and Henry Kissinger, one of Ms Rice's predecessors as Secretary of State, are two of the global figures to have been enlisted by the bank as part of the process, providing intriguing context to the HSBC board's decision to rule out moving to the US.

Reports had suggested that the bank was seriously looking at moving its headquarters to New York, but one source said on Thursday that the idea had always been a non-starter, partly because a US tax on dividends would hit HSBC's army of retail shareholders in Hong Kong.

Insiders said the bank had seriously looked at Canada, France and Hong Kong as an alternative to the UK.

It said last April that it would launch a formal review of the location of its headquarters in the wake of significant regulatory and tax reforms across the banking sector.

The review has been enormously complex, and has thrown up issues for the bank including the potential loss of its membership of London's blue-chip share index if it moves its headquarters back to Hong Kong after a 23-year absence.

Insiders say that the decision is finely balanced and that suggestions that HSBC was leaning in a particular direction were misguided.

Leading shareholders in the bank, including Martin Gilbert of Aberdeen Asset Management, say they expect it to remain domiciled in London.

George Osborne, the Chancellor, has demonstrated his keenness for the bank to remain based in the UK.

In his post-Election Budget, he altered the parameters of the Bank Levy, which costs HSBC far more annually than any of its rivals and which had been a growing source of frustration to the company's directors and investors.

The requirement for major lenders to establish ring-fenced subsidiaries by 2019 has also caused consternation on HSBC's board, which believes that the resultant separation of governance over the new entity will weaken its ability to make decisions about dividends and risk appetite.

Sources say the Bank Levy restructuring had not by itself represented "a tipping point" in persuading it to remain headquartered in the UK.

In a presentation to investors last June, Stuart Gulliver, HSBC's chief executive, said that criteria such as taxation and the ability to attract talent were among the factors that would shape the bank’s decision-making.

Mr Gulliver has made significant strides in restructuring HSBC since taking over in 2011, but has been frustrated by its lacklustre share price performance amid the low interest rate environment and the impact of increasingly onerous regulation.

He has sold scores of businesses and taken on thousands more compliance staff - adding significantly to its cost base - as oversight of the industry has intensified.

HSBC declined to comment on Ms Rice's involvement in its headquarters review, or on its progress.